This invention relates to an optical torque detecting apparatus for detecting torsional torque of a rotating shaft member, such as a power transmission shaft or the like provided in a power transmission system of a vehicle.
A known apparatus, as disclosed in Japanese Patent Application Publication Sho No. 57-4856, for instance, has a striped pattern comprising a group of constant pitched parallel lines affixed to an outer circumferential surface of a shaft member. A camera is provided with a negative having a similar pattern to the foregoing striped pattern positioned on a focal plane thereof. The camera is positioned so that an image of the striped pattern and the negative thereof are overlapped one with another so as to become equal in size. Stroboscopic lighting is effected once per one rotation of the shaft member by being synchronized with the rotation of the shaft member, so that a Moire fringe pattern corresponding to inclination of the striped pattern made in accordance with a torsion amount of the shaft member is created on the focal plane of the camera. Thus, the torsional torque of the shaft member may be detected from the inclined Moire pattern.
This type of apparatus, however, is inconvenient in that is becomes complicated in construction, because synchronizing the stroboscopic lighting with the rotation of the shaft member is required. Additionally, the detecting of torsional torque is made only at the time point of the stroboscopic lighting, so that the detecting time is limited.